182 research outputs found
Effect of Baffle Design on the Off-bottom Suspension Characteristics of Axial-flow Impellers in a Pilot-scale Mixing Vessel
The work aimed to determine the optimum system parameters for complete particle suspension. The experiments performed in a pilot-scale vessel (D = 1 m) were focussed on a study of the effects of geometrical vessel arrangements and, above all, on the effect
of alterations to the shape of the baffles.
The experiments sought above all to determine the critical impeller speed, ncr, and impeller power consumption, P, in a vessel equipped with non-standard, arrow-headed baffles, and also to compare these experimental data with results arising from measurements
undertaken in the same vessel, but equipped with four standard straight baffles.
Three types of axial-flow impellers were investigated, each of them in two sizes. The suspension volume fraction, , varied up to 10 %, with particle diameter from 0.1 to 3 mm.
The results aid the selection of the most favourable types of baffles and impeller giving the minimum power consumption and/or the minimum speed for just-suspended
particles. It is shown that the installation of arrow-headed baffles appears to be energetically more advantageous compared with the standard baffling
Residence Time Distribution of Solid Particles in a High-Aspect Ratio Multiple-Impeller Stirred Vessel
Despite its importance, experimental information on the Residence Time Distribution (RTD) of solid particles in continuous-flow stirred vessels is still scant. In this work, experimental data on particle RTD in a high-aspect-ratio vessel stirred by three equally-spaced Rushton turbines, was obtained by means of a special technique named Twin System Approach (TSA).
Quite surprisingly, results indicate that, among the various possibilities that could have been devised (e.g. 6, or 3, or 1 ideal tanks in series), the flow model closest to reality for the particle phase, at least in the experimental range here investigated, is that of a single perfectly stirred vessel
Pressure-induced polyamorphism in TiO2 nanoparticles
Machon, Denis Daniel, Marlene Pischedda, Vittoria Daniele, Stephane Bouvier, Pierre LeFloch, SylvieTwo different nanometric (6 nm) TiO2 compounds, anatase polycrystals and amorphous particles, were investigated under high pressure using Raman spectroscopy. Nanoanatase undergoes a pressure-induced amorphization. The pressure-induced transformations of this mechanically prepared amorphous state are compared with those of a chemically prepared amorphous particles. In the mechanically prepared amorphous state, a reversible transformation from a low-density amorphous state to high-density amorphous state (HDA1) is observed in the range 13-16 GPa. In the chemically prepared sample, a transformation to a new high-density amorphous state (HDA2) is observed at around 21 GPa. Further compression leads to the transformation HDA2 -> HDA1 at similar to 30 GPa. We demonstrate that depending on the starting amorphous material, the high-pressure polyamorphic transformations may differ. This observation indicates that pressure is a suited tool to discriminate between nanomaterials apparently similar at ambient conditions
High pressure behavior of CsC8 graphite intercalation compound
International audienceThe high pressure phase diagram of CsC8 graphite intercalated compound has been investigated at ambient temperature up to 32 GPa. Combining X-ray and neutron diffraction, Raman and X- ray absorption spectroscopies, we report for the first time that CsC8, when pressurized, undergoes phase transitions around 2.0, 4.8 and 8 GPa. Possible candidate lattice structures and the transition mechanism involved are proposed. We show that the observed transitions involve the structural re- arrangement in the Cs sub-network while the distance between the graphitic layers is continuously reduced at least up to 8.9 GPa. Around 8 GPa, important modifications of signatures of the electronic structure measured by Raman and X-ray absorption spectroscopies evidence the onset of a new transition
General boundary conditions for quasiclassical theory of superconductivity in the diffusive limit:application to strongly spin-polarized systems
Boundary conditions in quasiclassical theory of superconductivity are of
crucial importance for describing proximity effects in heterostructures between
different materials. Although they have been derived for the ballistic case in
full generality, corresponding boundary conditions for the diffusive limit,
described by Usadel theory, have been lacking for interfaces involving strongly
spin-polarized materials, such as e.g. half-metallic ferromagnets. Given the
current intense research in the emerging field of superconducting spintronics,
the formulation of appropriate boundary conditions for the Usadel theory of
diffusive superconductors in contact with strongly spin-polarized ferromagnets
for arbitrary transmission probability and arbitrary spin-dependent interface
scattering phases has been a burning open question. Here we close this gap and
derive the full boundary conditions for quasiclassical Green functions in the
diffusive limit, valid for any value of spin polarization, transmission
probability, and spin mixing angles (spin-dependent scattering phase shifts).
It allows also for complex spin textures across the interface and for channel
off-diagonal scattering (a necessary ingredient when the numbers of channels on
the two sides of the interface differ). As an example we derive expressions for
the proximity effect in diffusive systems involving half-metallic ferromagnets.
In a superconductor/half-metal/superconductor Josephson junction we find
junction behavior under certain interface conditions.Comment: 29 pages, 2 figures. More detailed explanations added, and a typo in
Equation (49) is corrected (factors 4 instead 2
Cardiac biomarkers of prognostic importance in chronic obstructive pulmonary disease
Background: Ischemic heart disease is common in COPD and associated with worse prognosis. This study aimed to investigate the presence and prognostic impact of biomarkers of myocardial injury and ischemia among individuals with COPD and normal lung function, respectively. Methods: In 2002â04, all individuals with airway obstruction (FEV1/VCâ<â0.70, nâ=â993) were identified from population-based cohorts, together with age and sex-matched non-obstructive referents. At re-examination in 2005, spirometry, Minnesota-coded ECG and analyses of high-sensitivity cardiac troponin I (hs-cTnI) were performed in individuals with COPD (nâ=â601) and those with normal lung function (nâ=â755). Deaths were recorded until December 31st, 2010. Results: Hs-cTnI concentrations were above the risk stratification threshold of â„5âng/L in 31.1 and 24.9% of those with COPD and normal lung function, respectively. Ischemic ECG abnormalities were present in 14.8 and 13.4%, while 7.7 and 6.6% had both elevated hs-cTnI concentrations and ischemic ECG abnormalities. The 5-year cumulative mortality was higher in those with COPD than those with normal lung function (13.6% vs. 7.7%, pâ<â0.001). Among individuals with COPD, elevated hs-cTnI both independently and in combination with ischemic ECG abnormalities were associated with an increased risk for death (adjusted hazard ratio [HR]; 95% confidence interval [CI] 2.72; 1.46â5.07 and 4.54; 2.25â9.13, respectively). Similar associations were observed also among individuals with COPD without reported ischemic heart disease. Conclusions: In this study, elevated hs-cTnI concentrations in combination with myocardial ischemia on the electrocardiogram were associated with a more than four-fold increased risk for death in a population-based COPD-cohort, independent of disease severity
Feasibility of an in situ measurement device for bubble size and distribution
The feasibility of in situ measurement device for bubble size and distribution was explored. A novel in situ probe measurement system, the EnviroCamâą, was developed. Where possible, this probe incorporated strengths, and minimized weaknesses of historical and currently available real-time measurement methods for bubbles. The system was based on a digital, high-speed, high resolution, modular camera system, attached to a stainless steel shroud, compatible with standard Ingold ports on fermenters. Still frames and/or video were produced, capturing bubbles passing through the notch of the shroud. An LED light source was integral with the shroud. Bubbles were analyzed using customized commercially available image analysis software and standard statistical methods. Using this system, bubble sizes were measured as a function of various operating parameters (e.g., agitation rate, aeration rate) and as a function of media properties (e.g., viscosity, antifoam, cottonseed flour, and microbial/animal cell broths) to demonstrate system performance and its limitations. For selected conditions, mean bubble size changes qualitatively compared favorably with published relationships. Current instrument measurement capabilities were limited primarily to clear solutions that did not contain large numbers of overlapping bubbles
Alteration of ribosome function upon 5-fluorouracil treatment favors cancer cell drug-tolerance.
Mechanisms of drug-tolerance remain poorly understood and have been linked to genomic but also to non-genomic processes. 5-fluorouracil (5-FU), the most widely used chemotherapy in oncology is associated with resistance. While prescribed as an inhibitor of DNA replication, 5-FU alters all RNA pathways. Here, we show that 5-FU treatment leads to the production of fluorinated ribosomes exhibiting altered translational activities. 5-FU is incorporated into ribosomal RNAs of mature ribosomes in cancer cell lines, colorectal xenografts, and human tumors. Fluorinated ribosomes appear to be functional, yet, they display a selective translational activity towards mRNAs depending on the nature of their 5'-untranslated region. As a result, we find that sustained translation of IGF-1R mRNA, which encodes one of the most potent cell survival effectors, promotes the survival of 5-FU-treated colorectal cancer cells. Altogether, our results demonstrate that "man-made" fluorinated ribosomes favor the drug-tolerant cellular phenotype by promoting translation of survival genes
Spin-polarized supercurrents for spintronics: a review of current progress
During the past 15 years a new field has emerged, which combines
superconductivity and spintronics, with the goal to pave a way for new types of
devices for applications combining the virtues of both by offering the
possibility of long-range spin-polarized supercurrents. Such supercurrents
constitute a fruitful basis for the study of fundamental physics as they
combine macroscopic quantum coherence with microscopic exchange interactions,
spin selectivity, and spin transport. This report follows recent developments
in the controlled creation of long-range equal-spin triplet supercurrents in
ferromagnets and its contribution to spintronics. The mutual proximity-induced
modification of order in superconductor-ferromagnet hybrid structures
introduces in a natural way such evasive phenomena as triplet
superconductivity, odd-frequency pairing, Fulde-Ferrell-Larkin-Ovchinnikov
pairing, long-range equal-spin supercurrents, -Josephson junctions, as
well as long-range magnetic proximity effects. All these effects were rather
exotic before 2000, when improvements in nanofabrication and materials control
allowed for a new quality of hybrid structures. Guided by pioneering
theoretical studies, experimental progress evolved rapidly, and since 2010
triplet supercurrents are routinely produced and observed. We have entered a
new stage of studying new phases of matter previously out of our reach, and of
merging the hitherto disparate fields of superconductivity and spintronics to a
new research direction: super-spintronics.Comment: 95 pages, 23 Figures; published version with minor typos corrected
and few references adde
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